Improvements in sample preparation, separation, and mass spectrometry continue to expand the coverage in LC-MS based lipidomics. While longer columns packed with smaller particles in theory give higher separation performance compared to shorter columns, the implementation of this technology above commercial limits has been sparse due to difficulties in packing long columns and successfully operating instruments at ultrahigh pressures. In this work, a liquid chromatograph that operates up to 35 kpsi was inve stigated for the separation and identification of lipid species from human plasma. Capillary columns between 15 -50 cm long were packed with 1.7 µm BEH C18 particles and evaluated for their ability to separate lipid isomers and complex lipid extracts from human plasma. Putative lipid class identifications were assigned using accurate mass and relative retention time data of the eluting peaks. Our findings indicate that longer columns packed and operated at 35 kpsi outperform shorter columns packed and run at lower pressures in terms of peak capacity and numbers of features identified. Packing columns with relatively high concentration slurries (200 mg/mL) while sonicating the column resulted in 6 -34% increase in peak capacity for 50 cm columns compared to low er slurry concentrations and no sonication. For a given analysis time, 50 cm long columns operated at 35 kpsi provided a 20 -95% increase in chromatographic peak capacity compared with 15 cm columns operated at 15 kpsi. Analysis n σ times up to 4 h were evaluated, generating peak capacities up to 410 ± 5 ( = 3, measured at 4 ) and identifying n 480 ± 85 lipids ( = 2). Importantly, the results also show a correlation between the peak capacity and the number of lipids identified from a human plasma extract. This correlation indicates that ionization suppression is a limiting factor in obtaining sufficient signal for identification by mass spectrometry. The result also shows that the higher resolution obtained by shallow gradients overcomes possible signal reduction due to broader, more dilute peaks in long gradients for improving detection of lipids in LC-MS. Lastly, longer columns operated at shallow gradients allowed for the best separation of both regional and geometrical isomers. These results demonstrate a system that enables the advantages of using longer columns packed and run at ultrahigh pressure for improving lipid separations and lipidome coverage.

Sosa-Montes de Oca, C., de Lange, G.J., Martínez-Ruiz, F., Ortega-Huertas, M., Rodríguez-Tovar, F.J., 2020. Microscale trace-element distribution across the Cretaceous/Palaeogene ejecta layer at the Agost section: Constraining the recovery of pre-impact conditions. Chemical Geology 533, 119431.

http://www.sciencedirect.com/science/article/pii/S0009254119305601 A high-resolution, sub-mm scale analysis of the distribution of major and trace elements across the ejecta layer marking the Cretaceous/Palaeogene boundary (KPgB) at the Agost section (SE Spain) was performed using Laser Ablation-Inductivity Coupled Plasma-Mass Spectrometry (LA-ICP- MS). A KPgB interval ≈17 mmthick, has been selected for this study. It includes gray calcareous marl from the uppermost Maastrichtian (Cretaceous), 2.02-mm-thick red clay (the ejecta layer), and blackish-gray clay (boundary clay layer) from the lowermost Danian (Palaeogene). The unconsolidated sediments were resin-embedded under O -free conditions 2 and analyzed by LA-ICP-MS line continuous scan measurements at 20 μm increments and a laser -beam of 120 μm. These micron -scale analyses show that the anomalous contents of trace and major elements in this boundary are restricted to the eje cta layer, which displays a relatively uniform distribution over its ≈2 mm thickness. Trace and major elemental ratios, such as Ca/Al, Ti/Al, Cr/Al, Fe/Al, Ni/Al, Cu/Al, Zn/Al, As/Al, Sb/Al and Pb/Al have similar values below and above the ejecta layer, consistent with similar palaeoenvironmental conditions prior to and after the impact event. Such element distribution points to anomalies exclusively restricted to the ejecta, thus a nearly instantaneous re-establishment of pre-impact conditions right after the impact event is observed.

Sosdian, S.M., Babila, T.L., Greenop, R., Foster, G.L., Lear, C.H., 2020. Ocean carbon storage across the middle Miocene: a new interpretation for the Monterey Event. Nature Communications 11, 134.

https://doi.org/10.1038/s41467-019-13792-0 The Miocene Climatic Optimum (MCO, 14 -17 Ma) was ~3-4 °C warmer than present, similar to estimates for 13 2100. Coincident with the MCOis the Monterey positive carbon isotope (δ C) excursion, with oceans more 12 13 depleted in C relative to C than any time in the past 50 Myrs. The long -standing Monterey Hypothesis uses this excursion to invoke massive marine organic carbon burial and draw-down of atmospheric CO as a cause 2 for the subsequent Miocene Climate Transition and Antarctic glaciation. However, this hypothesis cannot